Pupin-loaded long-distance cable with phantom formation



July 2, 1929. K .KUPFMULLE-R v 1,719,478

PUPIN LOADED LONG DISTANCE CABLE lWITH PHANTOM FORMATION Filed Nov. 19T1927 BOTH TYPES Cans/Neo //v ONE CAsLE Patented July 2, 1929.

UNITED -STATES PATENT OFFICE.

xARL KPEMLLER, or BEELIN-scHoNEBERG, GERMANY, AssIGNoE To SIEMENS aHALsxE AKTIENGESELLSCHAFT, or SIEMENssTAnT, NEAR BERLIN, GERMANY, A

PUPIN-LOADED LONG-DISTANCE CABLE WITH PHANTOM FORMATION.

Application filed November 19, 1927, Serial No. 234,452, and in GermanyFebruary 3, 1927.

This invention relates to electrical current transmission andpartlcularly to the transmission of= slgnahng currents through circuitsformed into a cable.

- In loade'd telephone cables quads of multiple twin formation, in whichthe two wires of eac-h pair are twisted together and then the pairstwisted into a quad, have been used almost exclusively. In such a. cablethe capac- .10 ity in the phantom circuits C2 is related approximatelyto the capacity in the .pairs C,l as

C, C1 1.6 to 1.7 Thus, there is a definite relation between theproperties of the side circuits and those of the phantom circuits. If,for instance, the cut-ofi` frequency of the side circuits and theattenuation ofthe side circuits and phantom circuits are fixed, then,ofcourse, the cut-oli' frequency for the phantom circuits has a 'delinitevalue.

If the ratio were to equal Zand the same attenuation maintained in theside an'd phantom circuits, then the phantom and side vcircuits willhave approximately the same C cut-off frequency. With the ratio of equalgood between the capacity in the phantom and side circuits:

.If lin this case the attenuation in the phan tom and side'circuits areequal, and the cutoff frequency of y'the side circuits so chosen that itis suliicientffor the distances which are to'be spanned, then thephantom c1rcu1t .r cable.

will have a` cut-olf frequency which is too low and the phantom circuitwill be practically unserviceable for telephony. As a matter of fact ithas been customaryl to construct spiral quadded telephone cable with thephantom circuits not loaded at all, the phantom circuits having beenused, if at all, for subordinate purposes only, such as telegraphy.

An object of this invention is to utilize the various circuits of thedifferent quads contained in a single cable so that each circuit andtype of and eiiiciently in accordance with-the varying number ofcircuits andcircuit lengths. Since the phantom circuit oflone type ofquad is serviceable over a longer distance than the side circuits of thesame type, and vice versa, for the other type of quad above mentioned,this invention relates tothe arrangement and use of the circuits of acable according to these relations. Other types of quads and singlepairs ma :also be contained in the In describing the invention'reference will be made to the drawings in which Fig. 1 showsqualitatively the relationship 'between the cut-off frequency and thecapacity ratios;

F ig.2 shows the relationship between the number of circuits and theirlengths.

Fig. 3 illustrates thecomparison between the ell'ect of the variousdegrees of loading for a given geographical spacing of loading points.

Fig. 4 shows a multiple twin quad; and

Fig. 5 shows a spiraled quad.

In Fig. 1 the graphical relation between the cut-off frequency for thephantom circuits and the ratio of the capacities between phantom andside` circuits is shown for agiven quad is used most economically,

cut-olil fre uency for the sidecircuits. The I d'enite cut-olf frequencyfor the side circuits Which is the same `as that for the phantomcircuits wheny the'` capacity ratio of is 1 equal to 2.' When this ratiois 1.7 as for multiple twin quads, and the cut-ofi fre-A quency of the.side circuits is the^ same'as above mentioned-and shown by the line C,then the lcut-off frequency for the phantom y a definite number ofquads.

therefore,fthat the number of phantom cir-` v5() from 1.7 to 2.7.

The curve in Fig. 2 represents how the number o f circuits for a giventraiic problem varies with the length of the circuits. Let us assumethat the transmission lengths lie between 150 and 5,000 km., and thatthe number of required circuits of any particular length is inaccordance with this curve, then the areaA under the curve representsthe total number of lines between 150 and 5,000 km. It is seen that thegreater number occurs at a length of about 500 km.

It is well known that with increasing length of circuit, the cut-oft'frequency of the line must also be increased if the same satisfactorytransmission is to be maintained. It is also well known that for thesame transmission level the cost per unit length of line increasesvwiththe increase in cut-off frequency. Now, although it is preferable from atheoretical standpoint to have a different cut-off frequency'for eachlength of circuit, in practice it becomes advantageous to limit thenumber of cut-off frequencies' to a rather small number.

If we assume that a cut-off frequency of about 2,600 cycles per secondis suitable for a l400 km. circuit, and that the side circuits of themultiple twin quads have this cut-off frequency, then the phantomcircuits of this type of quad may have a range of 800 km.

However, as shown in Fig. 2 about twice as many lines are needed in therange of lengths from 400 to 800 km. as in the range from 150 to 400km., while only half as many phantomcircuits asside circuits areavailable with cuits serving the number of circuits between 400 to-800km. is not nearly adequate. The phantom circuits may be exhausted by thecircuits having a len th of from 400 to 500 km. and for distances a ove500 km. a new type of line must beinsertcd.- However, the use ofmultiple twin quads for distances over 500 km. is favored since thenumber of circuits decreases 'as the distance increases.

In order to provide a cable vin which the various types of circuits areused to the best economical advantage, both spiraled and multiple twinquads are combined in one cable and the side and phantom circuits of lboth types ofquads are loaded. The lines may beloaded in any well knownmanner It is obvious,`

with either double coils or with combined coil systems. c

-Referring to Fig. 3 the attenuation in the circuits is plotted againstfrequency for heavy, medium and extra light loaded circuits and forcircuits not loaded at all based on a given geographical spacing ofloading points. For purposes of illustration cut-off frequencies of2,600, 3,600 and 5,000 cycles per second have been given for thc heavy,medium and extra light loaded circuits, respectively. From these curvesit is seen'that the cut-off frequency'occurs at lower frequencies forthe heavier loaded circuits than for lighter loaded ones although theloss over the usable frequency range increases as the loading becomeslighter. For the shorter systems, therefore, the heavier loaded linesare more practical while the lighter loaded lines are necessary for thelonger circuits.

In this invention it is desirable to so load the types of quads that forthe shorter length circuits spiraled quads are available, while for thelonger lengths multiple twin quads may be used. If it is not desired tobe limited to these two types of circuits, still other types may beadded for intermediate distances and it may be desirable according tocertain circumstances to use either only spiraled or multiple twin quadsor again a mixture of quads according to both types. In each case theratio of mixing the spiraled and multiple twin quads -and the method ofloading the whole cable is so chosen that the number of lines presentfor the various ranges is suffi# 10o cient to meet the actual trailicrequirements.

The advantage of a cable made according to this invention will now beexplained by way of an actual example assuming that again I the numberof circuits to be provided is in accordance with the curve shown in Fig.2.

Previously, the case discussed was where there were multiple twin quadswhose side circuits were sufficient for connections of a length up to400 km. and whose phantom circuits had a range up to 800 km., but wereonly suiiicient to meet the requirements of the number of circuits below500 km. in range. A more practical distribution is obtained when,according to the invention, spiraled quads are used for the shorterdistances, the phantom circuits being so loaded that they have a rangeof 400 km. Serving over a short distancethese circuits may be veryheavily loaded. Now, if the side circuits in ranges and if the range ofthe phantom circuits is to be 5,000 km. itwould be possible to countlona range of 2,500 km. for\th es1de circuits. These side and phantomcircuits are only lightly loaded since they are long dis-- tancecircuits. The number of side circuits will now suiiice to meet therequirements for connections from about 1,600l to 2,500 km. For the meanrange of 750 to 1,600fkm. a third type ofconductor may be used. Ifspiraled quads are used, however, and the phantom circuits are so loadedthat their range is about 900 km. and their number is sufficient forconnections between .7 50 to y900 km., then vthe number-of side circuitswhich is twice .as

great is suiiicient `for connections from 900 to 1,600 km.

A s the ranges of the variously stranded and variously loaded cablesoverlap each other, it

is possible to suitthe various operating conditions wit-hinsubstantially Wide limits. v lVhat is claimed is:

. 1. In a telephone cable,l spiraled quads forming phantom and sidecircuits, and multiple twm quads forming phantom and side circuits, saidside circuits and said phantom lcircuits being loade 2. In afcommunication cable, spiraled quads forming phantom and side circuitsand multiple twin quads forming phantom and side circuits, said phantomcircuits of said multiple twin quads being lightly loadedand saidphantom circuits of said spiraled quads `being heavily loaded.

3, 'In a communication cable,l spiraled quads forming phantom and sidecircuits and multiple-V twin quads forming phantom and sideclrcuitspsaid multiple twin quad circuits being lightly loaded and usedfor the longer distances while the spiraled quad circuits are heavilyloaded and used for the shorter disy tances. i

4. In a' communication cable, spiraled"4 4quads forming phantom and sidecircuits and multiple twin quads forming phantom and side circuits, acertain number of said side clrcuits of said multiple twin quads beinglightly loaded, and a certain number of said phantom circuits ofsaidspiraled quads Abeing 'heavilyloaded 5. In a loaded cable, spiraledquads forming phantom and side circuits, multiple twin quads formingphantom and side circuits and pairs of single circuits, said spiraleduads being used for the shorter distances and eavily loaded, saidymultiple twin quads being used for the loaded, while said pairsare`used for intermediate distances. y f- 'f 6. A method of utilizing acommunication cable having a plurality of multiple twin quads of phantomand side circuits and having. a plurality-of spiraled and side circuitscomprising, first, using said phantom circuits of said spiraled 'quads'for the shortest circuits oflsaid' cable,v second, using said sidecircuits o ffsaidspiraled quads for the. next length circuits, third,using ysaid side circuits of said multiple twip quads'for the thirdlength circuits, and/fourth, using said Iphantom circuits of saidmultiple twin quads for the longest-circuits. u

7. A method of utilizing a communication cable in acc'ordancelwithclaimfi in which' the multiple twinquad 'circuits are lightly loaded andthe spiraled quad -circuits'a're heavily loaded.

'greater distances and lightly quads of phantom f my namenthis 20 day ofOctober A, D., 1927,. A

KARL KPFMLLER

